Greatly valued for its durability, high compressive strength, and fire-resistance, concrete is one of the world's oldest and most used man-made building materials. In its simplest form, it consists of three main components: aggregates such as sand, gravel and crushed stone; a binder such as Portland cement; and water. Once these components have been mixed, the concrete must be quickly delivered to its intended location, before it hardens and becomes impossible to pour.
Because concrete production is time-sensitive, various methods and devices have been developed over the years for producing and transporting concrete to its ultimate destination in a quick and efficient manner. Central mixing, or wet-batch, concrete production is a method in which all of the ingredients are weighed and mixed in a stationary plant before being discharged to a truck that transports the wet concrete mixture to the construction site. Transit mixing is a method in which all the dry ingredients are weighed at the stationary plant and then charged into a truck that mixes the ingredients as they are being transported to the construction site, where water is added. In shrink mixing, mortar ingredients (sand, cement, water, and admixtures) are added, and the coarse aggregates are added as the mortar is discharged to the truck. All of these methods have certain advantages and disadvantages. Central mixing is generally recognized as allowing better quality control and faster production, but is not practical for all construction sites. The complexity of the plant makes portable set up more costly and time consuming. Transit mixing plants are generally less complex and less costly to operate, but standard transit mix plants do not have a concrete mixer, removing some of the advantages of the product quality control. Shrink mixing plants retain the product control that central mix gives, and allow the batch size to be increased and the mixing time to be decreased. By performing the final mixing in the revolving drum mixer truck or other transport unit, the plants allow for potentially higher production rates.
Some attempts have been made to design mobile mixing plants that allow concrete to be mixed and poured at the construction site. However, most of these plants have required a large number of individual components, such as bins and mixers, which are typically transported on separate trucks and assembled together at the site. The time and labor involved in transporting and installing these plants can be prohibitive. The volumetric trucks that are capable of mixing concrete in one complete unit do not provide concrete quality control required for all structural applications.
Another problem associated with modern-day concrete production is that Portland cement is produced in large, fossil fuel-burning kilns that create air pollution and emit large amounts of carbon, contributing significantly to global warming. As a result, various alternative binders such as environmentally friendly geo-polymer cements are growing in popularity. These cements require the use of activators and various other additives that require the use of additional bins and tanks. Current cement trucks and mobile mixing plants are not configured to accommodate these extra containers.
The above problems and other problems are addressed by this disclosure as summarized below.